EP 1805238 discloses polypropylene copolymers which shall contain maleic acid anhydride groups. No reaction of this polymer with polyamides is disclosed.
DE 3504804 discloses hot melt compositions, which comprise blends of polyamides and ethylene/acrylate ester copolymers which comprise additionally anhydride groups. The disclosed ethylene/acrylate ester copolymers have a molecular weight of more than 80000.
EP 0678543 discloses a copolymer consisting of a styrene block copolymer for example SEBS, which contains maleic acid anhydride groups. On this styrene block copolymer polyamide blocks are grafted.
WO 93/09175 discloses a blend of a polyamide, an unmodified polyolefin copolymer and a carboxyl-grafted terpolymer of ethylene, propylene and diene. No reaction of the polyamide and the terpolymer is disclosed.
WO 2009/138679 discloses a grafted copolymer made of polyamide and polyolefins. The polyamides are disclosed as Nylon-type polyamide PA-6, PA-11, PA-12 or similar types with a low molecular weight, the polyolefins are specified in the examples as ethylene-acryl(meth)acrylate-copolymer. The viscosity of the end product is disclosed as more than 600 Pa*sec.
The prior art discloses that blends of polyamides and polyolefins are difficult to mix and to obtain a stable blend needs specific measures. One possibility to improve the compatibility of these polymer types is introducing carboxylic groups in the polyolefin. Another way to obtain these mixtures includes the reaction of a polyamide and specific modified polyolefins but as disclosed this reaction provide high viscosity products. So the different proposals to manufacture stable blends require the selection of specific polymers and phase separation can occur. Phase separation often leads to insufficient adhesive properties to different substrates.
The technical interest in these polymer blends is still given, as polyamides show good cohesion properties. But as such adhesive layer often does not have sufficient adhesion to polyolefin substrates such composition need further improvement.